The Zero runs on lithium-ion batteries rather than gas. As a result, the engine doesn't make any noise. Before the safety bracelet, riders would dismount, forget they left the engine running, and send the bike on a ghost ride after accidentally twisting the throttle. The bracelet flips the key to the off position.

I handled the throttle with extreme caution on my test ride. I almost ran over Saiki, but that was due to driver incompetence. More on that later.

The Scotts Valley, Calif.-based company hopes to ride the growing interest in green vehicles with a line of electric two-wheelers. The company's first model, the Zero X for dirt bikes, can already be bought directly from the company for around $6,900. Google co-founder Larry Page bought one.

Video:
CNET News.com's Michael Kanellos stops by to take a look at one of Zero Motorcycles' bikes and take it for a test drive.

In the next few months, Zero Motorcycles will try to come out with a street-legal commuter motorcycle that will be slightly larger and more powerful than the Zero X (along with having the lights and turn signals necessary for street riding). Later, it will follow with a scooter.

But Motorcycles have drawn fewer entrants. Vectrix has released an all-electric scooter with nickel batteries that costs $11,000, and a few other companies have touted newer versions of the electric bike. Major manufacturers and venture capitalists, however, have not yet flocked to the field.

Zero executives, though, assert that motorcycles may be a better fit when it comes to battery-powered vehicles. At $6,900, the bike will be comparable with many 250cc gas-burning motorcycles.

"We're selling a bike that outperforms the ones with gas engines at the same price, and the price is going down," said acting CEO Damon Danielson.

The Zero X will only go 40 miles on a single charge, far less than a gas bike and less than the 70-mile Vectrix. Still, that's enough for most motocross drivers and street-bike commuters, and the street version will go farther. The average U.S. driver only goes about 25 miles to 30 miles a day, according to several studies.

The battery can be recharged in two hours. Motocross professionals also can buy a spare battery for $2,500.

Compare that to the commuter car coming from Think. The car will go about 100 miles on a charge, but it is expected to cost around $35,000 before the battery lease. Tesla will have a sedan in 2009 that will go about 200 miles, but these will cost probably close to $70,000. Electric cars take about three to five hours to fully charge.

Will a 40-mile motorcycle be accepted by consumers while $35,000 cars that have trouble doing a quick San Jose-San Francisco loop be rejected? No one knows, but Zero can at least claim it is eroding the price delta more rapidly than other electric vehicle vendors.

Approximately 1.1 million motorcycles are shipped to U.S. customers annually, according to the Motorcycle Industry Council. Worldwide, motorcycle sales account for $45 billion in sales, according to Danielson.

Getting a bike certified for street riding is somewhat simple, Danielson added. For Zero to convert a motocross bike into a street machine only requires a few modifications, such as adding turn signals and lights. Safety certification and testing takes about 9 to 12 months and costs about $100,000, he said.

Testing a new car involves several crash tests and prototype testing, a process that can consume years and millions of dollars.

Transportation agency officials "figure with motorcycles, you are on your own," Saiki said.

Helicopters to cycles
Saiki has worked on various transportation problems for years. Among other projects, he headed up a group that built the DaVinci IV, a human-powered helicopter and a prop plane for NASA that reached 80,000 feet. He's also designed mountain bikes for, among others, Trek and Santa Cruz Cycles.

Like other electric vehicles, the key to the Zero is the battery pack. The lithium-ion cells in the battery come from a third-party manufacturer, which sells the same cells to the power tools industry. Zero, though, arranges the cells in a particular way to prevent runaway thermal reactions, the phenomenon that causes notebooks to explode. Saiki would not go into technical detail, but said patents are pending on the battery pack. If major manufacturers like Honda get into the market, Saiki said, Zero will likely try to market its battery to them.